The invention relates generally to the field of electrical drives. More particularly, the invention relates to techniques for detecting utility AC input grounding conditions for the drive.
Various power systems include power conversion systems such as electric drives and motors which are employed to convert electrical energy into mechanical energy. An electric drive includes a device or group of devices which controls the torque, speed, position, and/or performance of an electric motor. The drive is typically connected to a power source such as a battery, a power supply, or an AC generator, and controls the transmission of power from the power source to the motor, which converts the electrical power into mechanical power.
Electrical drives may be used for a wide range of industrial applications. For example, different types of electrical systems use electrical drives to drive power to various types of motors, such as AC induction motors, servomotors, DC motors, etc., which each perform different motions, such as rotary or linear motion under torque, velocity or position control, etc. The system configurations for such different applications and different mechanical functions may also vary greatly. For instance, different electrical systems may use different grounding configurations, such as solid grounded Y, solid grounded Δ (also referred to as corner grounded), high resist ground (HRG) grounded Y, or ungrounded, etc. The installation or configuration of an electrical drive is generally different depending on the grounding configuration of the system. An HRG system involves inserting a resistance between a neutral node and the ground of the input AC source of the system such that the system can operate under single ground faulted condition with a small non-destructive ground fault current.
Typically, improperly configuring an electrical drive according to the grounding configuration of the electrical system results in unexpected drive failure, as discussed in the Mar. 19-23, 2006 IEEE APEC article, Failure Mode for AC Drives on High Resistance Grounded Systems, by Rangarajan M. Tallam, et al. For example, HRG faults may result in high voltage levels in bus lines associated with the electrical drive and high voltage stresses in electrical drive components, which may eventually result in failures of the electrical drive or other system components. Moreover, HRG faults are typically difficult to detect once a drive is in operation, as the small amount of fundamental frequency ground current is difficult to measure in the presence of high frequency electronic noise created by the drive, especially in larger electrical drives. It is now recognized that techniques for reducing electrical drive configuration errors based on the grounding configuration of the electrical system may reduce such HRG fault conditions. The present techniques involve identifying a HRG system and other properties of the HRG system to determine the drive configuration.